JP2001-263475A, published by the Japan Patent Office in 2001, discloses a belt continuously variable transmission (“CVT”). The belt CVT can change its speed ratio by changing the groove width of pulley around which a belt is wrapped. Changing the groove width is performed by adjusting hydraulic pressure supplied to a hydraulic cylinder provided in a rear surface of the pulley by using a speed ratio control valve. A stepping motor drives the speed ratio control valve.